NASA
points out something is always burning on Earth. Wildfires are started by
lightning or accidentally by people, and people use controlled fires to manage
farmland and pasture and clear natural vegetation for farmland. Fires can
generate large amounts of smoke pollution, release greenhouse gases, and
unintentionally degrade ecosystems. But fires can also clear away dead and dying
underbrush, which can help restore an ecosystem to good health. In many
ecosystems, including boreal forests and grasslands, plants have co-evolved with
fire and require periodic burning to reproduce.

Temperature,
precipitation levels, and soil moisture are turning many of our forests into
kindling during wildfire season. As the climate warms, moisture and
precipitation levels are changing with wet areas becoming wetter and dry areas
becoming drier.

Higher
spring and summer temperatures and earlier spring snow-melt typically cause
soils to be drier for longer, increasing the likelihood of drought and a
longer wildfire season, particularly in the western United States.

These hot,
dry conditions also increase the likelihood that, once wildfires are started
by lightning strikes or human error, they will be more intense and
long-burning.

The costs of
wildfires, in terms of risks to human life and health, property damage, and
state and federal dollars, are devastating, and they are only likely to
increase unless we better address the risks of wildfires and reduce our
activities that lead to further climate change.

Wildfires are
already on the rise.

Wildfires in
the western United States have been increasing in frequency and duration
since the mid-1980s, occurring nearly four times more often, burning more
than six times the land area, and lasting almost five times as long
(comparisons are between 1970-1986 and 1986-2003).

Natural
cycles, human activities—such as land-use (clearing, development, mining)
and fire exclusion—as well as climate change can influence the likelihood of
wildfires. However, many of the areas that have seen these increases—such as
Yosemite National Park and the Northern Rockies—are protected from or
relatively unaffected by human land-use and behaviors. This suggests that
climate change is a major factor driving the increase in wildfires.

• What is the
relationship between precipitation patterns, global warming, and wildfires?

While
severe wildfires have been observed to occur more frequently and this trend
is projected to continue throughout the 21st century, it is worth noting
that not every year has an equal likelihood of experiencing droughts or
wildfires.

Natural,
cyclical weather occurrences, such as El Niño events, also affect the
likelihood of wildfires by affecting levels of precipitation and moisture
and lead to year-by-year variability in the potential for drought and
wildfires regionally.

Nonetheless,
because temperatures and precipitation levels are projected to alter further
over the course of this century, the overall potential for wildfires in the
United States, especially the southern states, is likely to increase as
well.

• As the world
warms, we can expect more wildfires

Wildfire
seasons (seasons with higher wildfire potential) in the United States are
projected to lengthen, with the southwest’s season of fire potential
lengthening from seven months to all year long. Additionally, wildfires
themselves are likely to be more severe.

Researchers
and modelers project that moist, forested areas are the most likely to face
greater threats from wildfires as conditions grow drier and hotter.

Surprisingly, some dry grassland areas may be less at risk, but not because
they would be flourishing—the intense aridity is likely to prevent these
grasses from growing at all, leaving these areas so barren that they are
likely to lack even the fodder for wildfire.

• A
conflagration of costs

The economic
costs of wildfires can be crippling. Between 2000 and 2009, the property
damages from wildfires averaged $665 million per year.

In addition
to the property damage they wreak, wildfires cost states and the federal
government millions in fire-suppression management; the U.S. Forest
Service’s yearly fire-suppression costs have exceeded $1 billion dollars at
least twice since FY 2000.

The risk to
property owners at the “wildland-urban interface” in California (more than 5
million homes in southern coastal California, the Bay Area, and north of
Sacramento) is projected to increase with the increase in wildfires near
these areas.

The
environmental and health costs of wildfires are also considerable: not only
do wildfires threaten lives directly, but they have the potential to
increase local air pollution— exacerbating lung diseases and causing
breathing difficulties even in healthy individuals.

Additionally, a counterintuitive aspect of wildfires—especially in the
semi-arid southwest United States—is that when the rains do come, mountain
forest wildfires increase flash flood risk in lower-lying areas in the days
and months following the fire due to loss of vegetation and the inability of
burned soil to absorb moisture (PDF). For example, residents in Arizona
living along usually dry stream beds have lost property and life following
such tragic and unexpected post-wildfire flash floods.

• What can we
do to address the threat of wildfires?

The global
temperature is increasing and the climate is changing due to the
greenhouse-gas emissions we have already produced, leading to a likely rise
in the incidence of wildfires.

But it is
not too late. What we do now has the power to influence the frequency and
severity of these fires and their effects on us.

By engaging
in mitigation efforts—creating buffer zones between human habitation and
susceptible forests, and meeting home and city fire-safety standards—and by
taking steps to reduce our impact on the climate, we can help to keep our
forests, our homes, and our health safe.

The global
warming mitigation method addresses the threat of wildfires by moving the heat
that is increasing their likelihood to a more benign location.